The major long-term objectives are: 1. To search for functional evidence of local control mechanisms within the utero ovarian vascular complex in rhesus monkeys which may be involved in the transfer of hormones or other materials between the uterus and ovary and thus serve to regulate corpus luteum function. 2. To relate rate and distribution of blood flow within the uteroovarian vascular loop to the varying levels of corpus luteum activity found during the menstrual cycle, several stages of pregnancy and lactation. Current experiments in progress are designed to (1) determine if a local vascular pathway is required for the transfer of materials from the uterus to the ovary containing the corpus luteum during early pregnancy, (2) evaluate the relative blood flow to the corpus luteum during varying levels of functional activity, and (3) investigate the possible importance of arterio-venule shunting of blood at different levels of corpus luteum activity.